Catelyn arrives at King Renly's camp to negotiate an alliance, and Brienne of Tarth wins the right to join Renly's guard. Catelyn and Brienne witness Renly's murder at the hands of dark magic sent by the Red Lady Melisandre, an emissary of Renly's brother and rival claimant to the Iron ThroneStannis Baratheon. Catelyn and Brienne flee Renly's camp and rejoin Robb's army as Renly's supporters switch their allegiance to Stannis. Meanwhile, Theon betrays the Starks by siding with his father and seizing Winterfell by force. Robb receives news of Theon's plans and sends men to retake Winterfell, while inside the city the Starks' allies form plans to sneak Bran and Rickon Stark out.

Robb learns that his mother Catelyn has secretly freed Jaime Lannister, now escorted by Brienne of Tarth, in order to ransom her daughters Sansa and Arya; he also enters into a romantic relationship with Volantene healer Talisa Maegyr. Yara Greyjoy arrives at Winterfell to bring Theon back to the Iron Islands, after his botched attempt to recapture the Stark boys.

Tywin Lannister leaves Harrenhal, which allows Arya, Gendry and Hot Pie to make an escape with the help of the enigmatic Jaqen H'ghar. In King's Landing, Cersei attempts to blackmail Tyrion by abducting the prostitute, Ros, whom Cersei believes to be his secret lover. Leading the defense against Stannis' attack on King's Landing, Tyrion destroys many of the attacking craft with an exploding ship full of wildfire, and is forced to lead a counterattack as King Joffrey Baratheon and his bodyguard Sandor Clegane each desert the battlefield. Stannis's forces make it inside the castle, but Tyrion leads his men behind the Baratheon forces via underground tunnels and attacks. Baratheon is defeated when Tywin's forces arrive at King's Landing shortly after.

Following Khal Drogo's death, Daenerys and the remnants of her khalasar find refuge in the city of Qarth, where they are taken in by the merchant Xaro Xhoan Daxos. However, Xaro conspires with the warlock Pyat Pree to kill most of Daenerys' servants, kidnap her dragons and assume control of Qarth. Daenerys is lured into a showdown with Pyat Pree at the House of the Undying, where her dragons kill Pyat Pree. Daenerys seals Xaro in his own vault as punishment for his treachery and leaves Qarth with Jorah and her remaining servants.

Whilst on a ranging beyond the Wall, Jon Snow captures a Wildling, Ygritte, who soon leads him into a trap where he himself is captured by Ygritte's fellow wildlings. Amongst the wildlings' prisoners is fellow ranger Qhorin Halfhand, who convinces Jon to kill him in order to gain the wildlings' trust so he can get close to their leader, King-beyond-the-Wall Mance Rayder. The rest of the rangers set up camp at an ancient fortification, the Fist of the First Men, where they come under attack from an ancient enemy, the White Walkers.

HBO ordered a second season of Game of Thrones on April 19, 2011, two days after the series premiere.[4] The second season obtained a 15% increase in budget in order to be able to stage the war's most important battle,[5] the Battle of the Blackwater, in episode nine.

Filming took place during 106 shooting days. During three-quarters of those, two crews ("Dragon" and "Wolf") were working simultaneously in different locations.[6]

The casting for the second season began in May 2011.[7] Although a large portion of the first season cast were returning, the producers were still faced with a huge number of new characters to be cast. The producers decided that several characters from A Clash of Kings, including the Freys and Crannogmen Reeds at Winterfell, Frey bannermen of the Starks, the Tullys, Stannis' wife and daughter, Theon's uncle Aeron Greyjoy and the bastard Ramsay Snow would not be cast despite appearing in the novel. ShowrunnersDavid Benioff and D.B. Weiss commented on this saying that certain character introductions taking place in A Clash of Kings would be delayed until the third season. This was done due to the large number of characters already introduced in season two, and because they couldn't afford to have people "waiting around" for their characters to become central to the plot.[8] Having to fill so many speaking roles, the showrunners not only "postponed" the introduction of several key characters, but they also merged some into one, or certain plot-functions were given to different characters. Many physical traits were also altered, such as the ethnicity or age of characters. The cast was estimated to be the largest on television.[9] Scattered around two fictional continents characters include, by order of importance:

Emerging as the fourth claimant to the throne is the estranged brother of the late king Robert, Stannis Baratheon (Stephen Dillane).[10] The foreign priestess Melisandre, portrayed by Carice van Houten poses as an influential, yet manipulative advisor to Stannis. Van Houten was previously asked (but unable) to audition for the role of Cersei in season one. While her character retains her signature red robes and hair, unlike in the novels Melisandre is not portrayed as having red eyes, making her appear somewhat more human.[11]Liam Cunningham stars as Ser Davos Seaworth, the "Onion Knight", a bannerman of Stannis and a former smuggler.[12] Cunningham had already been in talks for a role in the first season. As he is left-handed, his Davos has the fingers of the right hand shortened, unlike in the novels where his left hand is crippled. In an interview, Cunningham said that a lot of new dialogue had to be written for his character, because in the novels Davos, a point-of-view character, is portrayed more through his thoughts than through his actions.[13] These three characters headed a new storyline set on a different location, that by the end of the season merged with the main plot.

Theon Greyjoy (Alfie Allen), a main cast member from the first season, but with lesser importance than the others, came to prominence during the second season, as his story unfolded and his character become more central. Gemma Whelan appeared as his sister, Yara Greyjoy. Named "Asha" in the novels, the character's name was changed to avoid confusion with the Wildling Osha, Bran Stark's companion.[14] "Asha" is portrayed as a fairly provocative and independent woman, a captain of thirty ships, as opposed to her television counterpart Yara, who did not retain "Asha's" traits, although her rivalry with Theon remained intact. Their father Balon Greyjoy was played by Patrick Malahide.[15] Many of the characters involved in the Greyjoys' storyline weren't introduced, most notably Balon's brother Aeron Greyjoy. Nonetheless, the storyline received enormous praise, with the alternation of Yara's name and persona being the only criticism.

Tom Wlaschiha is cast as Jaqen H'ghar, a mysterious prisoner who develops a murderous relationship with young Arya Stark (Maisie Williams).[16] Wlaschiha's pronunciation of his character's name, Jack-in, was adopted for use in the show.[17]Natalie Dormer, best known for her portrayal as seductive Anne Boleyn in Showtime's The Tudors, was cast in a similar role as Margaery Tyrell, a noblewoman and the wife of the third claimant to the throne, Renly Baratheon.[18]Gwendoline Christie played, to much praise, Brienne of Tarth, a female warrior who joins Renly Baratheon's guard, but later becomes a follower of Catelyn Stark.[19] To prepare for the role, Christie took up an intense training regimen, adding over a stone (6.4 kg) of muscle mass.[20] So that she could be mistaken for a man, her armor was decorated with lines that slant away from her hips.[21] On the other side of the fictional world, two female roles with rising prominence were added to the cast: Skins star Hannah Murray filled the role of Craster's daughter Gilly, a love interest to Samwell Tarly;[22] while the second role, the one of Ygritte, Jon Snow's love interest among the Wildlings, was played by Rose Leslie.[23]

Daenerys Targaryen's (Emilia Clarke) stay at Qarth, opened the way for several recurring characters. Nonso Anozie played Daenerys's host at Qarth, Xaro Xhoan Daxos.[24] The character differed a lot from his novel counterpart. Xaro's homosexuality, femininity and caucasian origin were overshadowed by dark skinned Anozie's masculinity and heterosexuality. Acting as one of her suitors is the treacherous warlock Pyat Pree portrayed by Ian Hanmore. Her third and final suitor was the masked priestess Quaithe (Laura Pradelska). Specially created for the television series was the so-called "Spice King", a rich merchant from Qarth, played by Nicholas Blane. Also an original creation of the show is the character of Talisa (Oona Chaplin), a healer from Volantis and a romantic interest for Robb. She fills the role of another female interest of Robb's, called Jeyne Westerling, who has no similarities with Talisa whatsoever. In addition to Talisa, Michael McElhatton joins the cast in the role of Roose Bolton, an important character in Robb Stark's storyline. Lastly, Simon Armstrong plays the legendary Night's Watch ranger Qhorin Halfhand.

Others were also added to the cast, either in a small recurring role or with reduced prominence. The most notable example is Tony Way's Ser Dontos Hollard, a drunkard knight, who had a pivotal role in Sansa Stark's storyline that ran in the course of two books, while in the series the role was reduced to a small scene in the opening episode. Others include: Ben Crompton as "Dolorous Edd" Tollet, a man of the Night's Watch.[25]Robert Pugh as the Wildling Craster, father and husband to Gilly.[26]Kerr Logan as Davos Seaworth's pious son Matthos.[27]Karl Davies as Ser Alton Lannister, a character created for the series[28] who replaces Cleos Frey as envoy from the Starks to the Lannisters. Daniel Portman took the role of Podrick Payne, the squire to Tyrion Lannister.[29] The 19-year-old Portman plays Podrick as about 16 years old, instead of about 12 as in the novels. To be able to portray Podrick as awkward, shy and weak, Portman, previously a sportsman, stopped his fitness regimen and gained some weight to appear more endearing.[30]Lucian Msamati played Salladhor Saan, a Lysene pirate and friend of Davos Seaworth. Finally, Edward Dogliani appeared briefly as the "Lord of Bones" (or "Rattleshirt" in the novels), a Wildling leader and Oliver Ford Davies as Stannis's maester Cressen.[31]

All of the recurring characters from the first season returned, with one notable exception: Conan Stevens, whose role of Gregor Clegane was recast with Ian Whyte, did not return.[32]Roy Dotrice, a friend of George R.R. Martin, known for reading the audio versions of the books and having previously rejected a role due to health reasons, appears this season as Pyromancer Hallyne, an elderly alchemist at King's Landing.[33]

For the second season, the city of Dubrovnik, Croatia, was used instead of Malta for scenes in King's Landing and elsewhere.[34] Scenes set north of the Wall were filmed in Iceland, on the Vatnajökull glacier, in November 2011.[35] New shooting locations in Northern Ireland include The Linen Mill Film & Television Studios in Banbridge, Ballintoy Harbour[36] and Downhill Strand.

HBO released numerous teaser trailers for the second season, beginning on December 11, 2011.[37] The second trailer, published on January 29, 2012,[38] was viewed 3.5 million times in the first three days after publication, a record for HBO promotional content.[39] Other trailers were released on February 24,[40] March 3 (set to Florence and the Machine's Seven Devils)[41] as well as subsequently.

To Cersei's dismay, Tyrion takes up his post as acting Hand at King's Landing. At Dragonstone, Stannis Baratheon proclaims allegiance to Melisandre's new god and lays public claim to the Iron Throne, revealing Joffrey's bastardry. As this news reaches the capital, the Gold Cloaks slaughter Robert's bastards. Having won three victories, Robb Stark offers the Lannisters peace in exchange for the North's independence, sending Theon to gain Balon Greyjoy's support and Catelyn to seek Renly Baratheon's. Beyond the Wall, the Night's Watch find shelter with the WildlingCraster and his daughter-wives. In Essos, as her people slowly die in the Red Waste, Daenerys sends out riders to look for help.

Returning to his home of Pyke after nine years as the Starks' ward, Theon Greyjoy is reunited with his sister, Yara, and his father, Balon, who despises Theon for his Northern ways and intends to win back his crown by force. Cersei rejects Robb Stark's terms and Tyrion exiles Janos Slynt, head of the Gold Cloaks, to the Wall, promoting Bronn to commander of the watch. On the road to the Wall, Arya reveals her true identity to Gendry. North of the Wall, Samwell Tarly is approached by one of Craster's daughters, Gilly, who is pregnant and fears for her unborn child; Jon is reluctant to help her despite Sam's pleas. In the Red Waste one of the horses returns to Daenerys with the severed head of its rider in a pouch, a message from one of her enemies. On Dragonstone, Davos Seaworth recruits the pirate Salladhor Saan to Stannis's side, and Stannis has sex with Melisandre to obtain the son his wife cannot give him. Jon discovers that Craster sacrifices his sons to the White Walkers.

Catelyn Stark arrives at King Renly's camp to negotiate an alliance, and the woman warrior Brienne of Tarth wins the right to join Renly's guard. Tyrion crafts a plan to find who is in Cersei's confidence by proposing three different marriages to the members of the Small Council. At Winterfell, Bran Stark needs help to decipher his dreams. On the road to the wall, the band of Night's Watch recruits are attacked by Lannister soldiers. Yoren is killed and Arya is taken prisoner.

Catelyn tries to convince the Baratheon brothers to abandon their quarrel and unite against the Lannisters, while Sansa is abused by Joffrey in revenge for her brother's victories. Tyrion intervenes and in return, Joffrey is cruel to his "gifts". Arya and Gendry are taken captives to the castle of Harrenhal. After her exhausting journey through the desert, Daenerys arrives at the gates of the prosperous city of Qarth. Melisandre gives birth to a shadow creature.

In Harrenhal, Jaqen H'ghar, one of the three caged prisoners Arya Stark saved from death during her trip to the Wall pledges to kill three people of her choosing in order to repay his debt to her. She accepts and chooses the Tickler as the first, the man who tortures to death the captives that were brought there with her. After Renly's sudden death at the hands of Melisandre's shadowy assassin, Catelyn and Brienne are forced to flee from Renly's camp. Theon sails from Pyke prepared to prove that he is a true Ironborn, with plans to overtake Winterfell while Robb is out fighting the war. The Night's Watch arrive at an ancient fortress called the Fist of the First Men, where they intend to make a stand.

Princess Myrcella is sent away from King's Landing. Theon Greyjoy's plans to take Winterfell succeed as he continues to try to prove his Ironborn status. Robb reunites with the healer Talisa. At the Fist of the First Men, the ranger Qhorin Halfhand gives Jon Snow the opportunity to prove his worth. While out on patrol, Jon takes prisoner a Wildling named Ygritte. Joffrey incites a riot at King's Landing, in which he is nearly killed and Sansa is nearly raped. At Qarth, Daenerys tries to procure a ship to take her people to Westeros. Taken in by Tywin Lannister, Arya attempts to hide that she is Ned Stark's daughter, as Jaqen H'ghar helps her conceal her identity. Robb receives news of Theon's plans and sends men to retake Winterfell, while inside the city there are plans to get Bran and Rickon out. Daenerys' dragons are stolen.

Theon tries to track Bran and Rickon with hounds. After an assassination attempt, Tywin Lannister begins searching Harrenhal for his potential murderer. Ygritte continues her attempts to seduce Jon and, after a momentary lapse in Jon's concentration, she escapes and leads him into a trap. Still shaken from the riot, Sansa is horrified when she awakens to find that she has had her first period, and can thus bear Joffrey's children. In Robb's camp, a failed escape attempt by Jaime leaves a guard dead, and Catelyn worries about the camp's desire for retribution. In Qarth, the warlock Pyat Pree reveals to Daenerys that he stole her dragons, but gives her the opportunity to reunite with them before slaughtering the Council of Thirteen and establishing Xaro Xhoan Daxos as king of Qarth. Theon presents to Maester Luwin and his subjects the charred corpses of two boys, informing them that he has tracked down and killed Bran and Rickon Stark.

Robb Stark learns that his mother Catelyn has secretly freed Jaime Lannister, now escorted by Brienne of Tarth, in order to ransom her daughters Sansa and Arya; he also enters into a romantic relationship with Talisa. Yara Greyjoy arrives at Winterfell to bring Theon back to Pyke, after his botched attempt to recapture the Stark boys. Tywin Lannister leaves Harrenhal to attack Robb, which leads Arya Stark, Gendry and Hot Pie to attempt an escape with the help of Jaqen H'ghar, who agrees to help in order for Arya to refrain from naming H'ghar himself as the third man to kill. In King's Landing, Cersei Lannister attempts to blackmail Tyrion by abducting the prostitute, Ros, whom Cersei believes to be his secret lover. The capital prepares for assault by Stannis, who, underway to King's Landing, promises to make Davos Seaworth his Hand of the King. Beyond the Wall, the Wildling leader "Rattleshirt" leads the captured Jon Snow and Qhorin Halfhand to his king, Mance Rayder. In Qarth, Jorah Mormont agrees to accompany Daenerys into the House of the Undying to retrieve her dragons. In a secret location, Osha schemes to get Bran and Rickon Stark, who are revealed to be very much alive, to safety.

Stannis Baratheon's fleet assaults King's Landing in the Battle of Blackwater Bay. Leading the defense, Tyrion Lannister destroys many of the attacking craft with an exploding ship full of wildfire, and is forced to lead a counterattack as King Joffrey and his bodyguard Sandor Clegane each desert the battlefield. Stannis' forces make it inside the castle, but Tyrion leads his men behind the Baratheon forces via underground tunnels and attacks. Meanwhile, Queen Regent Cersei, holed up in the fortress with Sansa Stark and the other ladies of the court, succumbs to wine and despondency as she believes the battle lost. In the nick of time, as she is about to poison her son Tommen, Tywin Lannister's forces, joined by Loras Tyrell, the lover of Renly Baratheon, arrive to dispatch the attackers.

The aftermath of the Battle of the Blackwater sees Joffrey set Sansa aside in favor of marrying Margaery Tyrell while Tyrion fears for his and Shae's safety now that his father has replaced him as Hand of the King. Melisandre gives the defeated Stannis a new hope. Brienne runs into trouble while escorting Jaime to King's Landing. Catelyn tries to convince Robb that his romance with Talisa is dangerous, but he defies her and the two are married. In Qarth, Daenerys ventures into the House of the Undying and successfully retrieves her dragons. She then seals the traitor Xaro Xhoan Daxos inside his own vault and claims his riches for herself to buy a ship. In Winterfell, Theon is betrayed by his own men in the face of an inevitable siege while Winterfell is put to the torch. Osha and Hodor sneak brothers Bran and Rickon away from the smoldering ruins and take them North toward the Wall. Arya, having escaped Harrenhal with Hot Pie and Gendry, receives the gift of a valuable coin from Jaqen. North of the Wall, Qhorin Halfhand forces Jon to kill him to prove his loyalty to the Wildlings and an army of White Walkers surrounds the Fist of the First Men.

Thanks to the critical and commercial success of the first season, as well as HBO's marketing efforts, the second season received intensive media coverage well before it started airing. Sunday is Coming, a two-minute short film for Funny or Die, satirized viewers' excitement about the return of Game of Thrones.[54]

Several media outlets reviewed the season's first four episodes before they were broadcast, and rendered almost uniformly positive verdicts. The season holds a Metacritic score of 90 out of 100, indicating "universal acclaim".[55]

Entertainment Weekly rated the new season "A-" and praised the "vivid, vital, and just plain fun" storytelling. In the reviewer's opinion, the greatly enlarged cast did not feel like bloat and the show remained accessible to those who had not read the novel.[56]The Huffington Post called the start of the second season "far more elegant and engaging" than that of the first, and appreciated the show's maturation, increased assurance and momentum as well as the visually improved settings and the new actors' performance.[57]Newsday '​s review gave it an "A+", calling it the "best show on television" and warranting the preparation required by viewers.[58]

The Hollywood Reporter also wrote that Game of Thrones made a "strong case for being one of TV's best series". Impressed that the series continued to improve in quality as it breathed life into its vast web of interconnected storylines, the reviewer considered that, unlike other genre shows, Game of Thrones had gravitas such that it should not be considered dramatically inferior to shows like Mad Men or Breaking Bad.[59]HitFix '​s Alan Sepinwall gave the new, "bigger and better" season an "A", praising its increased confidence and smoothness despite its even greater use of "sexposition".[60] New to the series, the Chicago Sun-Times '​s reviewer found the season premiere "engrossing" and praised the "top-notch" acting, writing, sets and storytelling.[61] The New York Times was the only major publication to publish a mixed review. It criticized the lack of complexity in the characters apart from Dinklage's, the confusing multitude of characters and the meandering plot.[62]

DVD/Blu-ray box sets and digital downloads of the second season were released in North America on February 19, 2013. The DVD set contains a 30-minute feature covering the production of the episode "Blackwater", actor interviews, character profiles, twelve audio commentaries by cast and crew, and a discussion about Westerosi religions by the showrunners and George R.R. Martin. The Blu-ray set additionally contains a feature about the "War of the Five Kings" that breaks out in season two, as well as 19 animated histories of the mythology of Westeros and Essos.[64]

The music for the second season, again composed by Ramin Djawadi, was published as a soundtrack album in June 2012. It contains a rendition of a song often mentioned or sung in the novels, The Rains of Castamere, by the indie rock band The National.[65]